Field of Invention
This invention relates to the design of sound reproduction elements in audio headphones.
Description of Prior Art
Audio headphones are typically designed with diaphragm elements of a compression driver design. These elements produce sound like conventional speakers which generate compression waves from a mechanical diaphragm driven by an electrical signal from an amplifier. Typically, the diaphragm elements are arranged inside the headphone housing so that compression waves are directed straight to the ear. U.S. Pat. No. 7,162,051 to Grell, et al (2007) discloses a headphone design in which the transducer is mounted so that the compression waves are directed into the ear. This arrangement can cause listening fatigue as well as hearing loss from high sound levels.
Most headphones are designed with one diaphragm element which is expected to reproduce the frequencies within the range of human hearing. This is often stated to be between 20-20,000 hertz. These diaphragm elements often cannot accurately reproduce the entire range without some distortion occurring. U.S. Pat. No. 4,418,248 to Mathis (1983) discloses a dual transducer design which divides the audio spectrum between the two transducers. The transducers are also mounted to direct the compression waves into the ear, putting stress on the ear drum.
The haptic effect as it applies to sound reproduction is the physical sensation of sound as well as the hearing of sound. Audiences of live concerts with higher volume levels often experience this “felt” sound, particularly from lower frequencies such as a bass drum beat. This effect is not reproduced very well in conventional headphone design due to the typical low mass of the diaphragm elements. U.S. Pat. No. 8,767,996 to Lin, et al (2014) discloses a headphone design incorporating a haptic transducer in the head band and in the ear pad housings in another drawing. The haptic transducers are not shown to be connected to a resonator assembly and are directed into the ear from the ear pad housings.